Both are iconic for their respective genres, we can't compare them to each other.

Respective genres? I do understand that Adele is able to branch into soul music but they are still both generally POP music. They can be compared and in context to the question, 21 is more iconic than Teenage Dream.

Teenage Dream is iconic and global

Teenage Dream crowned Katy as the Female MJ so that.

21 is more global than TT thats for sure

21 Easily.. But I've enjoyed TD more.. It was fun and NOT depressing.

Teenage Dream

It's not the matter or sales. We have enough Diamond or 20 million+ selling album. But how many album with 6 #1 singles we have?

What is TT

Tik Tok?

Teenage Dream has set the bar high for modern pop music, it has become the example to follow. The singles will remain as staples (radio keeps playing them all) with iconic imagery to back them up.

Not enough in the digital era, no.

I know Adele can be considered as Pop, but more as a serious way of Pop (Pop and Soul ballads) while Katy is all about this rock, funny and bubblegum pop.

People will never take serious the Pop Music that girls like Gaga, Rihanna or Katy make. While they'll embrace and acclaim Adele's music because they consider it "art".

So, 21 has become iconic as a piece of Pop Art. And for the colorful and bubblegum pop, TD is iconic too.